Synthetic resin binders, such as phenol-formaldehyde, added in the manufacture of fiberboard, such as hardboard and particle board, represent a substantial portion of the coat of manufacture. Many attempts have been made to substitute all or a portion of such synthetic resin binders with less expensive components. For example, attempts have been made to utilize lignin-containing spent digestion liquors to form binding resins capable of bonding fibers and fibrous particles in the formation of a fiberboard, as set forth in U.S. Pat. Nos. 2,849,314 and 3,095,392. As set forth in the Guss U.S. Pat. No. 2,849,314, in spite of the many processes proposed for obtaining resinous compositions from sulfite liquor, for the most part such products have found little or no commercial application as thermosetting impregnating agents, binders or adhesives and particularly in the field of production of improved cellulosic and other fibrous materials.
In accordance with the Herrick U.S. Pat. No. 3,095,392, a lignosulfonate is added to a reacted mixture of phenol and formeldehyde to form a modified phenol-formaldehyde resin for use as a fluid loss control agent in drilling muds and portland cement slurries. In accordance with the Herrick method of manufacture of the lignosulfonate modified phenol-formaldehyde resins, the phenol and formaldehyde are permitted to react prior to the addition of the lignosulfonate.
In accordance with the principles of the present invention, it has been found that new and unexpected results are achieved in the formation of a lignosulfonate modified phenol-formaldehyde resin when the lignosulfonate is added to phenol and formaldehyde prior to a significant amount of reaction between the phenol and formaldehyde.